Should Patients with Kearns-Sayre Syndrome and Corneal Endothelial Failure Be Genotyped for a TCF4 Trinucleotide Repeat, Commonly Associated with Fuchs Endothelial Corneal Dystrophy?

The aim of this study was to describe the ocular phenotype in a case with Kearns-Sayre syndrome (KSS) spectrum and to determine if corneal endothelial cell dysfunction could be attributed to other known distinct genetic causes. Herein, genomic DNA was extracted from blood and exome sequencing was performed. Non-coding gene regions implicated in corneal endothelial dystrophies were screened by Sanger sequencing. In addition, a repeat expansion situated within an intron of TCF4 (termed CTG18.1) was genotyped using the short tandem repeat assay. The diagnosis of KSS spectrum was based on the presence of ptosis, chronic progressive external ophthalmoplegia, pigmentary retinopathy, hearing loss, and muscle weakness, which were further supported by the detection of ~6.5 kb mtDNA deletion. At the age of 33 years, the proband's best corrected visual acuity was reduced to 0.04 in the right eye and 0.2 in the left eye. Rare ocular findings included marked corneal oedema with central corneal thickness of 824 and 844 µm in the right and left eye, respectively. No pathogenic variants in the genes, which are associated with corneal endothelial dystrophies, were identified. Furthermore, the CTG18.1 genotype was 12/33, which exceeds a previously determined critical threshold for toxic RNA foci appearance in corneal endothelial cells.

The impact of biomechanics on corneal endothelium tissue engineering.

The integrity of innermost layer of the cornea, the corneal endothelium, is key to sustaining corneal transparency. Therefore, disease or injury causing loss or damage to the corneal endothelial cell population may threaten vision. Transplantation of corneal tissue is the standard treatment used to replace malfunctioning corneal endothelial cells. However, this surgery is dependent upon donor tissue, which is limited in supply. Hence, tissue engineers have attempted to construct alternative transplantable tissues or cell therapies to alleviate this problem. Nevertheless, the intrinsic non-dividing nature of corneal endothelial cells continues to foil scientists in their attempts to yield large numbers of cells in the laboratory for use in such novel therapies. Interestingly, the contribution of the biomechanical properties of the underlying extracellular matrix (ECM) on cell division, tissue development and maintenance has been extensively investigated in other many cell types. However, the impact of biomechanics on corneal endothelial cell behaviour is relatively unexplored. Here, we describe contemporary tissue engineering solutions aimed at circumventing donor tissue scarcity. We review the ECM structure and biomechanical features of corneal endothelial cells. We discuss the alterations of ECM in endothelial disease development and progression and point out the role of ECM in developing a tissue-engineered corneal endothelium. We highlight the main biomechanical cues, including topographical and mechanical features, that impact cellular behaviors. Finally, we discuss the influence of biomechanical cues on cell and tissue development, and how corneal endothelial cells response to individual biomechanical stimuli in tissue engineering, which have implications for designing an engineered endothelium and maintaining cell function.

Matrix metalloproteinases and their inhibitors in Fuchs endothelial corneal dystrophy.

Fuchs endothelial corneal dystrophy (FECD) is characterized by a progressive loss of corneal endothelial cells (CECs) and an abnormal accumulation of extracellular matrix in Descemet's membrane leading to increased thickness and formation of excrescences called guttae. Extracellular matrix homeostasis is modulated by an equilibrium between matrix metalloproteinases (MMPs) and their endogenous tissue inhibitors (TIMPs). This study aimed to investigate MMPs and TIMPs profile in FECD, taking into account cell morphology. Populations of FECD and healthy CECs were cultured and their conditioned media collected for analysis. The presence of proteases in the conditioned media was studied using a semi-quantitative proteome profiler array, and MMPs levels were assessed using quantitative assays (ELISA and quantitative antibody array). MMP activity was determined by zymography and fluorometry. The expression pattern of the membrane type 1-MMP (MT1-MMP, also known as MMP-14) was examined by immunofluorescence on ex vivo FECD and healthy explants of CECs attached to Descemet's membrane. Finally, MMPs and TIMPs protein expression was compared to gene expression obtained from previously collected data. FECD and healthy CEC populations generated cultures of endothelial, intermediate, and fibroblastic-like morphology. Various MMPs (MMP-1, -2, -3, -7, -8, -9, -10, and -12) and TIMPs (TIMP-1 to -4) were detected in both FECD and healthy CECs culture supernatants. Quantitative assays revealed a decrease in MMP-2 and MMP-10 among FECD samples. Both these MMPs can degrade the main extracellular matrix components forming guttae (fibronectin, laminin, collagen IV). Moreover, MMPs/TIMPs ratio was also decreased among FECD cell populations. Activity assays showed greater MMPs/Pro-MMPs proportions for MMP-2 and MMP-10 in FECD cell populations, although overall activities were similar. Moreover, the analysis according to cell morphology revealed among healthy CECs, both increased (MMP-3 and -13) and decreased (MMP-1, -9, -10, and -12) MMPs proteins along with increased MMPs activity (MMP-2, -3, -9, and -10) in the fibroblastic-like subgroup when compared to the endothelial subgroup. However, FECD CECs did not show similar behaviors between the different morphology subgroups. Immunostaining of MT1-MMP on ex vivo FECD and healthy explants revealed a redistribution of MT1-MMP around guttae in FECD explants. At the transcriptional level, no statistically significant differences were detected, but cultured FECD cells had a 12.2-fold increase in MMP1 and a 4.7-fold increase in TIMP3. These results collectively indicate different, and perhaps pathological, MMPs and TIMPs profile in FECD CECs compared to healthy CECs. This is an important finding suggesting the implication of MMPs and TIMPs in FECD pathophysiology.

Directed Differentiation of Human Pluripotent Stem Cells towards Corneal Endothelial-Like Cells under Defined Conditions.

The most crucial function of corneal endothelial cells (CEnCs) is to maintain optical transparency by transporting excess fluid out of stroma. Unfortunately, CEnCs are not able to proliferate in vivo in the case of trauma or dystrophy. Visually impaired patients with corneal endothelial deficiencies that are waiting for transplantation due to massive global shortage of cadaveric corneal transplants are in a great need of help. In this study, our goal was to develop a defined, clinically applicable protocol for direct differentiation of CEnCs from human pluripotent stem cells (hPSCs). To produce feeder-free hPSC-CEnCs, we used small molecule induction with transforming growth factor (TGF) beta receptor inhibitor SB431542, GSK-3-specific inhibitor CHIR99021 and retinoic acid to guide differentiation through the neural crest and periocular mesenchyme (POM). Cells were characterized by the morphology and expression of human (h)CEnC markers with immunocytochemistry and RT-qPCR. After one week of induction, we observed the upregulation of POM markers paired-like homeodomain transcription factor 2 (PITX2) and Forkhead box C1 (FOXC1) and polygonal-shaped cells expressing CEnC-associated markers Zona Occludens-1 (ZO-1), sodium-potassium (Na+/K+)-ATPase, CD166, sodium bicarbonate cotransporter 1 (SLC4A4), aquaporin 1 (AQP1) and N-cadherin (NCAD). Furthermore, we showed that retinoic acid induced a dome formation in the cell culture, with a possible indication of fluid transport by the differentiated cells. Thus, we successfully generated CEnC-like cells from hPSCs with a defined, simple and fast differentiation method.

Morphological change and recovery of corneal endothelial cells after rho-associated protein kinase inhibitor eye-drop (ripasudil 0.4%) instillation.

BACKGROUND/AIMS: To investigate the time-dependent change of corneal endothelial cell (CEC) morphology and density (CECD) in patients with glaucoma post instillation of rho-associated protein kinase inhibitor ripasudil (Rip) 0.4% eye drops. METHODS: This observational study involved 163 eyes of 163 patients with glaucoma in whom CEC morphological change was evaluated by CECD calculated via non-contact specular microscopy (NCSM) before and at 1 or 3 months post-Rip instillation. The change of CECD was plotted along with elapsed time from last instillation of Rip. The patients were divided into the following three groups based on the elapsed time post-Rip instillation: Early Group (<2 hours), Middle Group (≥2 hours, yet <6 hours) and Late Group (≥6 hours). The rate of CECD change was then analysed and compared among the three groups. An additional eight eyes of four patients with glaucoma were enrolled for a time-dependent study, with NCSM images evaluated before and at 1, 2, 3, 4 and 6 hours post-Rip instillation. RESULTS: Morphological changes in the CECs appeared within 1 hour and recovered to normal within 6 hours post instillation. In the Early, Middle and Late Group, the median rate of CECD change as calculated by the NCSM automated software was -5.68%, -4.95% and -0.07%, respectively. The CEC images showed the same morphological changes with observational study in all four cases. CONCLUSION: Due to transient morphological changes, the NCSM software produced misleading data for determining CECD within 1 hour post-Rip instillation, yet revealed that CEC morphology gradually recovered to normal within 6 hours.

Femtosecond Laser-Assisted Cataract Surgery: Does It Improve Outcomes in Fuchs Endothelial Corneal Dystrophy?

The role of femtosecond laser -assisted cataract surgery in patients with Fuchs endothelial corneal dystrophy remains poorly defined. This invited commentary examines the current evidence surrounding this often-debated topic.

Energy Shortage in Human and Mouse Models of SLC4A11-Associated Corneal Endothelial Dystrophies.

Purpose: To elucidate the molecular events in solute carrier family 4 member 11 (SLC4A11)-deficient corneal endothelium that lead to the endothelial dysfunction that characterizes the dystrophies associated with SLC4A11 mutations, congenital hereditary endothelial dystrophy (CHED) and Fuchs endothelial corneal dystrophy 4. Methods: Comparative transcriptomic analysis (CTA) was performed in primary human corneal endothelial cells (pHCEnC) and murine corneal endothelial cells (MCEnC) with normal and reduced levels of SLC4A11 (SLC4A11 KD pHCEnC) and Slc4a11 (Slc4a11-/- MCEnC), respectively. Validation of differentially expressed genes was performed using immunofluorescence staining of CHED corneal endothelium, as well as western blot and quantitative PCR analysis of SLC4A11 KD pHCEnC and Slc4a11-/- MCEnC. Functional analyses were performed to investigate potential functional changes associated with the observed transcriptomic alterations. Results: CTA revealed inhibition of cell metabolism and ion transport function as well as mitochondrial dysfunction, leading to reduced adenosine triphosphate (ATP) production, in SLC4A11 KD pHCEnC and Slc4a11-/- MCEnC. Co-localization of SNARE protein STX17 with mitochondria marker COX4 was observed in CHED corneal endothelium, as was activation of AMPK-p53/ULK1 in both SLC4A11 KD pHCEnC and Slc4a11-/- MCEnC, providing additional evidence of mitochondrial dysfunction and mitophagy. Reduced Na+-dependent HCO3- transport activity and altered NH4Cl-induced membrane potential changes were observed in Slc4a11-/- MCEnC. Conclusions: Reduced steady-state ATP levels and subsequent activation of the AMPK-p53 pathway provide a link between the metabolic functional deficit and transcriptome alterations, as well as evidence of insufficient ATP to maintain the Na+/K+-ATPase corneal endothelial pump as the cause of the edema that characterizes SLC4A11-associated corneal endothelial dystrophies.

Quantitative and Morphological Corneal Endothelial Changes After Selective Laser Trabeculoplasty and Retinal Photocoagulation.

PURPOSE: Selective laser trabeculoplasty (SLT) and retinal photocoagulation (RP) are two common laser procedures often performed at a wavelength of 532 nm, and may affect the corneal endothelium. This study used corneal specular microscopy to determine the impact of these procedures on the corneal endothelium. DESIGN: Retrospective cohort study in a private practice. METHODS: There were 249 eyes from 136 consecutive patients who underwent SLT for open-angle glaucoma and 132 eyes from 74 patients who underwent RP included. Corneal specular microscopy was performed immediately before and after each procedure and at 1-month postprocedure. Microscopy data included quantitative measures, such as cell density and central corneal thickness, and morphological measures, including percentage of hexagonal cells and coefficient of variation in cell area. RESULTS: There was a small (just over 1%) reduction in corneal endothelial cell count from pre-SLT to post-SLT (P = 0.008), and a statistically significant recovery at 1 month (P = 0.04). Central corneal thickness also transiently increased from pre-SLT to post-SLT (P = 0.03). Although polymegathism was unchanged, changes in pleomorphism were observed (P = 0.03). The only change in the RP group was an increase in polymegathism between pre-RP and post-RP (P = 0.001). CONCLUSIONS: SLT has measurable effects on both quantitative and morphological characteristics of the corneal endothelium, which seem to be transient. RP has fewer measurable effects, likely because, although the total laser energy is similar, it is delivered over a much longer time (3 ns versus 0.1 s). The changes observed in both procedures are minor and unlikely to be of clinical significance.

Descemet Stripping Endothelial Keratoplasty in Pediatric Patients with Congenital Hereditary Endothelial Dystrophy.

PURPOSE: To report the long-term outcomes of Descemet stripping endothelial keratoplasty (DSEK) with suture-assisted donor lenticule insertion performed in different age groups for pediatric patients with congenital hereditary endothelial dystrophy (CHED). DESIGN: Retrospective case series. METHODS: Pediatric patients with CHED who underwent DSEK from January 2010 to January 2016 were enrolled. Patients were divided into 2 groups according to their ages: the infant group and the child group. Long-term clinical outcomes and complications were compared. RESULTS: Thirty eyes of 16 patients were included: 19 eyes (10 patients) in the child group and 11 eyes (6 patients) in the infant group. The average duration of follow-up was 4.08 ± 1.90 years (range 2.5-8.5 years). Corneal transparency scores of the 2 groups on postoperative day 7 were not statistically different. The average postoperative best-corrected visual acuity (BCVA) in the infant group (logMAR 0.32 ± 0.11) was better than that in the child group (logMAR 0.54 ± 0.20; (P = .01). Thirty-three percent of cases in the child group and 86% of cases in the infant group had postoperative BCVA achieved or better than logMAR 0.4. Average endothelial cell loss in the child group was 31.21% ± 9.17%. Lenticule detachment occurred in 3 cases in the child group. CONCLUSIONS: Improved visual outcomes could be achieved in infant patients with CHED after DSEK without significant complications. Suture-assisted donor lenticule insertion techniques, Descemet membrane stripping, and postoperative sedation are advocated technical points.

Regeneration of the Corneal Endothelium.

Penetrating keratoplasty was the only therapeutic choice for the treatment of corneal endothelial decompensation until the introduction of evolutional endothelial keratoplasties, namely Descemet's stripping automated endothelial keratoplasty (DSAEK) and Descemet's membrane endothelial keratoplasty (DMEK). Although now in widespread use, DSAEK and DMEK still have associated problems, such as difficulty of the surgical technique, acute and chronic cell loss, and shortage of donor corneas. Therefore, regeneration of the corneal endothelium by tissue engineering techniques is being researched to overcome these problems. The concept of transplantation of cultured corneal endothelial cells (CECs) was proposed in the 1970s. However, cultivation of human CECs (HCECs) in sufficient quantity and with acceptable quality for clinical use has proven surprisingly difficult, and the development of methods for transplanting cultured HCECs has been necessary. Numerous research groups have developed culture protocols and techniques that are now bringing corneal endothelial regeneration closer to real-world therapy. For instance, we started a clinical trial in 2013 involving the injection of cultured HCECs into the anterior chamber of patients with corneal endothelial decompensation. This review outlines the rapid progression of this research field, including clinical trial results, and is also intended to identify topics that still require further research or discussion.

A Porcine Corneal Endothelial Organ Culture Model Using Split Corneal Buttons.

Experimental research on corneal endothelial cells is associated with several difficulties. Human donor corneas are scarce and rarely available for experimental investigations as they are normally needed for transplantation. Endothelial cell cultures often do not translate well to in vivo situations. Due to the biostructural characteristics of non-human corneas, stromal swelling during cultivation induces substantial corneal endothelial cell loss, which makes it difficult to perform cultivation for an extended period of time. Deswelling agents such as dextran are used to counteract this response. However, they also cause significant endothelial cell loss. Therefore, an ex vivo organ culture model not requiring deswelling agents was established. Pig eyes from a local slaughterhouse were used to prepare split corneal buttons. After partial corneal trephination, the outer layers of the cornea (epithelium, bowman layer, parts of the stroma) were removed. This significantly reduces corneal endothelial cell loss induced by massive stromal swelling and Descemet's membrane folding throughout longer cultivation periods and improves general preservation of the endothelial cell layer. Subsequent complete corneal trephination was followed by the removal of the split corneal button from the remaining eye bulb and cultivation. Endothelial cell density was assessed at follow-up times of up to 15 days after preparation (i.e., days 1, 8, 15) using light microscopy. The preparation technique used allows a better preservation of the endothelial cell layer enabled by less stromal tissue swelling, which results in slow and linear decline rates in split corneal buttons comparable to human donor corneas. As this standardized organo-typically cultivated research model for the first time allows a stable cultivation for at least two weeks, it is a valuable alternative to human donor corneas for future investigations of various external factors with regards to their effects on the corneal endothelium.

Fuchs Endothelial Corneal Dystrophy: Clinical, Genetic, Pathophysiologic, and Therapeutic Aspects.

Fuchs endothelial corneal dystrophy (FECD) is a bilateral corneal endothelial disorder and the most common cause of corneal transplantation worldwide. Professor Ernst Fuchs described the first 13 cases of FECD more than 100 years ago. Since then, we have seen far-reaching progress in its diagnosis and treatment. In the field of diagnostics, new technologies enable the development of more accurate classification systems and the more detailed breakdown of the genetic basis of FECD. Laboratory studies help in deciphering the molecular pathomechanisms. The development of minimally invasive surgical techniques leads to a continuous improvement of the postoperative result. This review highlights and discusses clinical, genetic, pathophysiologic, and therapeutic aspects of this common and important corneal disorder.

Changes in total, anterior, and posterior corneal surface higher-order aberrations after 1.8 mm incision and 2.8 mm incision cataract surgery.

PURPOSE: To evaluate changes in corneal higher-order aberrations (HOAs) on the anterior and posterior corneal surfaces after 1.8 mm microincision cataract surgery (MICS) and 2.8 mm small-incision cataract surgery (SICS). SETTING: Eye Department, First Affiliated Hospital, School of Medicine, Zhejiang University, China. DESIGN: Prospective case series. METHODS: Right eyes of patients had MICS or SICS. The preoperative and 1-week and 3-month postoperative distance visual acuity (CDVA) and dry eye-related indices were determined. The corneal total HOAs and Zernike coefficients (3rd and 4th order) over 4.0 and 6.0 mm zones, corneal volume, central corneal thickness (CCT), and anterior and posterior corneal astigmatism were measured using a Pentacam HR analyzer. RESULTS: The MICS group comprised 126 eyes and the SICS group 70 eyes. The MICS and SICS groups had similar postoperative CDVA; however, the MICS group had quicker recovery of CCT, corneal volume, and corneal astigmatism. Significantly increased anterior corneal total HOAs were observed in the SICS group over a 6.0 mm zone (P < .001). Both groups showed significantly increased posterior corneal total HOAs over both zones (P < .001). Similar changing patterns in individual Zernike terms were observed. The MICS group had quicker recovery of posterior corneal surface coma and trefoil than the SICS group, especially over the 6.0 mm zone. Changes in posterior corneal surface total HOAs were correlated with corneal volume changes (P < .01). CONCLUSIONS: The data suggest quicker corneal recovery and less change in total and anterior corneal surface corneal HOAs after MICS. Changes in posterior corneal surface HOAs were more pronounced in both surgical groups.

Endothelial dysfunction in a child with Pearson marrow-pancreas syndrome managed with Descemet stripping automated endothelial keratoplasty using a suture pull-through technique.

A 4-year-old girl with a history of Pearson marrow-pancreas syndrome presenting with severe, progressive photophobia was found to have bilateral, diffuse corneal thickening and peripheral pigmentary retinopathy. She underwent Descemet stripping automated endothelial keratoplasty (DSAEK) surgery in both eyes using a modified suture pull-through technique. Postoperatively there was no evidence of cataract formation or graft detachment; her corneas thinned, and her photophobia improved dramatically.

The Influence of Trabectome Surgery on Corneal Endothelial Cells.

PURPOSE: The purpose of this study was to evaluate the influence of trabectome surgery on corneal endothelial cells by site. METHODS: Retrospective observational study. Trabectome surgeries were performed on 159 eyes of 132 adult Japanese patients. Corneal endothelial cells were measured at the center (C), inferior (I), nasal inferior (NI), nasal superior (NS), superior (S), temporal superior (TS), and temporal inferior (TI) sectors at <1 month preoperatively and 3, 6, 12, 24, and 36 months postoperatively, for changes in corneal endothelial cell density (ECD), coefficient of variation (CV), and incidence of hexagonal cells (6A). RESULTS: Mean preoperative ECD in all groups were 2401±451 (SD) cells/mm (C), 2366±450 cells/mm (I), 2397±479 cells/mm (NI), 2476±554 cells/mm (NS), 2493±596 cells/mm (S), 2464±558 cells/mm (TS), and 2329±510 cells/mm (TI). The 12-month postoperative mean ECDs were 2344±480 cells/mm (C), 2312±469 cells/mm (I), 2325±536 cells/mm (NI), 2473±517 cells/mm (NS), 2438±607 cells/mm (S), 2227±578 cells/mm (TS), and 2193±523 cells/mm (TI). There was no change in ECD in all sectors before and after surgery. ECD decreased at the TS and TI in combination with cataract surgery (2620±430 and 2445±384 cells/mm) preoperatively to 2264±501 and 2216±477 cells/mm at 12 months postoperatively. CV and 6A did not change at all sites in all surgical procedures before and after surgery. CONCLUSIONS: Trabectome surgery involves minimal effects to corneal endothelial cells, although long-term prospective studies with greater sample sizes are necessary to confirm this conclusion.

A Rabbit Corneal Endothelial Dysfunction Model Using Endothelial-Mesenchymal Transformed Cells.

Unlike humans, rabbit corneal endothelial wounds are known to spontaneously heal. The current study was aimed to develop a new rabbit bullous keratopathy model using corneal endothelial cells that were induced to undergo endothelial-mesenchymal transformation (EMT). EMT was induced in rabbit corneal endothelial cells (RCECs) by culturing with TGFß and basic FGF Supplemented Medium. The corneal endothelia in recipient rabbits were mechanically scraped from the corneal endothelial surface inside an 8 mm mark. Then, a suspension of EMT-induced RCECs (EMT-RCECs) was injected into the anterior chamber. Eyes injected with freshly isolated RCECs (Fresh RCECs group) and eyes that were scraped without injection of cells (Scrape group) were used as controls. Immediately following operation, subepithelial and stromal edema was observed with increased central corneal thickness and corneal opacity in all groups. In the EMT-RCECs group, bullous keratopathy persisted for 42 days up to the end of the study. In the Fresh-RCECs and Scrape groups, corneal transparency and thickness recovered by 7 days after treatment and was maintained up to 42 days. The activated fibroblast marker, α-SMA, was observed spanning from corneal endothelium to corneal stroma in the EMT-RCECs group. Interestingly, α-SMA was upregulated in the Scrape-group as well. In all groups, there was no damage to other intraocular structures, and intraocular pressure was normal throughout the observation period. Transplanting a fresh donor cornea effectively treated corneal edema due to bullous keratopathy. This model is a promising tool for pre-clinical trials in the development of new therapies against corneal endothelial dysfunction.

Fuchs Endothelial Corneal Dystrophy Through the Prism of Oxidative Stress.

The corneal endothelium (CE) is vital for maintaining the water balance and clarity of the cornea. The CE is a cell layer that is particularly susceptible to aging because of its postmitotic arrest, high metabolic activity involving pumping of ions, and lifelong exposure to ultraviolet light. Despite gradual age-related cell loss, a sufficient number of CE cells are preserved during the lifespan of an individual. However, in conditions such as Fuchs endothelial corneal dystrophy (FECD), permanent loss of CE cells leads to corneal edema and loss of vision requiring corneal transplantation. FECD is a genetic and oxidative stress disorder manifested by abnormal cell-matrix interactions and expedited cellular aging culminating in cellular death. Because the endothelium has minimal replicative capacity in vivo and an inability to replace its genome, it is particularly prone to cumulative DNA damage acquired throughout life. In FECD, the underlying genetic defects make the CE genome even more vulnerable to this damage, to the point of causing mitochondrial dysfunction, mitochondrial membrane potential loss, and excessive mitophagy activation. Endogenous and exogenous intracellular stressors alter the synthetic footprint of CE cells, leading to endothelial-mesenchymal transition and secretion of aberrant extracellular matrix (in the form of guttae), resembling scar formation in other organs. In turn, the guttae or endothelial scars contribute to a vicious cycle of FECD pathogenesis and, by further inducing endothelial-mesenchymal transition and oxidant-antioxidant imbalance, perpetuate the molecular changes of the degenerating endothelium.

Fuchs Endothelial Corneal Dystrophy and Mitochondria.

Fuchs endothelial corneal dystrophy (FECD) is a bilateral progressive corneal endothelial disease characterized by guttae, which present as partial Descemet membrane thickening, inducing corneal edema at the final stage. Oxidative stress has been reported to play an important role in the pathogenesis of FECD. The electron transport chain and oxidative phosphorylation (oxphos) system in mitochondria are the main sources of endogenous oxidative stress, arising from superoxide generation through premature electron leakage to oxygen. In FECD, corneal endothelial cells have altered mitochondria with mitochondrial DNA damage, decreased oxphos proteins, and lower mitochondrial membrane potential. Mitochondrial dynamics and mitophagy comprise the organelle-level mitochondrial quality control system. Mitochondrial dynamics includes fusion and fission processes. When mitochondria are severely damaged, fission becomes the dominant process to remove damaged mitochondria. Mitophagy is a selective autophagy pathway that removes damaged mitochondria, and is triggered by mitochondrial membrane potential depolarization. In the FECD corneal endothelium, mitochondria have a fission-dominant morphology and low density through mitophagy upregulation because of quality control processes against altered mitochondria.

Negative impact of dextran in organ culture media for pre-stripped tissue preservation on DMEK (Descemet membrane endothelial keratoplasty) outcome.

PURPOSE: To assess the morphological and functional outcomes of Descemet membrane endothelial keratoplasty (DMEK) performed with pre-stripped tissue preserved in organ culture medium containing dextran compared to tissue preserved in dextran-free medium. METHODS: In this retrospective study, we reviewed the clinical records of 103 patients who underwent DMEK surgery with pre-stripped tissue in our department between June 2015 and September 2016. The endothelium-Descemet membrane layer was preserved in organ culture medium for a maximum of 48 h for all patients. For group 1, 49 endothelium-Descemet membrane (EDM) were stripped and preserved in medium 1 (dextran-free organ culture medium), while 54 EDM were stripped and preserved in medium 2 (organ culture medium supplemented with 6% dextran T-500) for group 2. Outcome measures included best-corrected visual acuity (BCVA), central corneal thickness (CCT), and endothelial cell density (ECD) of all eyes in both groups at three consecutive postoperative time points: 2 weeks, 6 weeks, and 6 months postoperatively. We also compared the repeat keratoplasty rates between the groups. RESULTS: Group 1 showed a statistically significant better BCVA compared to group 2 at each time point (p < 0.05). The percentage of grafts achieving 0.5 or better after 6 months in group 1 was 96% and in group 2, it was 66% (P < 0.001). CCT was significantly lower in group 1 compared to group 2 at 2 weeks and 6 months after surgery (p < 0.05). ECD was comparable between donor grafts before surgery but was significantly greater in groups 1 after 2 and 6 weeks (p < 0.05), but not after 6 months. Necessity for repeat keratoplasty (repeat DMEK, subsequent penetrating keratoplasty (PKP)) was significantly lower in group 1 (p < 0.05). CONCLUSIONS: Pre-stripped tissue for DMEK preserved in dextran-free medium led to better visual recovery, thinner postoperative corneas, a higher endothelial cell density, and a lower rate of repeat keratoplasty, indicating that dextran has an unfavorable impact on the preservation of pre-stripped DMEK tissue.

Descemet Membrane Endothelial Keratoplasty: Outcomes in the First Year of Experience.

OBJECTIVES: We aimed to report the clinical outcomes of Descemet membrane endothelial keratoplasty in our first year of experience. MATERIALS AND METHODS: Patients who underwent Descemet membrane endothelial keratoplasty at the Baskent University Faculty of Medicine, Department of Ophthalmology, between 2015 and 2016 were included in the study. Patient demographics, cause of endothelial dysfunction, best-corrected visual acuity, central corneal thickness, graft survival, follow-up duration, and intraoperative and postoperative complications were recorded. RESULTS: Five eyes of 5 patients (4 female, 1 male) with a mean age of 53.4 ± 12.7 years were included. Cause of endothelial dysfunction included corneal endothelial dystrophy in 3 patients, pseudophakic bullous keratopathy in 1 patient, and endothelial graft failure after previous penetrating keratoplasty in 1 patient. Pre-stripped Descemet membranes obtained from the Ankara State Hospital Eye Bank were used. Mean duration of postoperative follow-up was 7.4 ± 3.7 months. Mean preoperative Snellen best-corrected visual acuity and central corneal thickness were 0.24 ± 0.15 and 625.5 ± 97.4 µm. Mean best-corrected visual acuity increased to 0.67 ± 0.26 (P = .02) in the first month and to 0.84 ± 0.11 (P < .01) at the end of follow-up. Mean central corneal thickness decreased to 546.6 ± 28.4 µm (P = .03). Graft detachment was observed in 1 patient on the first postoperative day, and it was reattached successfully by injection of air into the anterior chamber. There were no intraoperative complications. All corneas were clear at the end of follow-up. CONCLUSIONS: Descemet membrane endothelial keratoplasty provides a new and exciting option for endothelial transplant and has the potential to become the primary procedure for surgical management of Fuchs endothelial dystrophy and corneal endothelial disease. Rapid visual rehabilitation with few and manageable complications and good visual outcomes are the major advantages of this procedure.